Vehicle transmissions convert rotation of an engine into rotation of a drive shaft. Transmissions provide different selectable gear ratios that vary the relationship between the input and output speeds. The input and output speeds are typically determined using input and output speed sensors.
An exemplary control system is shown in FIG. 1. A controller 4 and a transmission 5 are shown. The controller 4, such as a powertrain control module, delivers power from a power supply 6 to a transmission input speed sensor 7 (TISS) and a transmission output speed sensor 8 (TOSS), respectively, through a first wire W1. A TISS signal is output to a first sensing resistor R1 in the controller 4 through a second wire W2. A first voltage sensor VS1 generates a voltage signal to a calculating module 9. A TOSS signal is output to a second sensing resistor R2 in the controller 4 through a third wire W3. A second voltage sensor VS2 generates a voltage signal to the calculating module 9. This approach requires separate wires for power (W1), for the TOSS signal (W2) and for the TISS signal (W3). The use of separate wires adds cost, installation time and increased potential for warranty claims.